I have seen a diver with IPE twice in my life. In 1 case it was my own instructor we had to take out of a cave. Of course, under water we did not know what was wrong, only he shouted 'go out' in the loop and was not able to swim anymore. So we pulled him out. At surface he was wheezing like hell and we had to bring him out of the water. He was diving a non-CE ccr (I heard from others that the WOB of this quite popular machine would never pass the CE-tests, but don't know if this is true, I haven't dived it myself). The diver was quite old, but for his age fit (did other cardio-sports). After being on surface and 45minutes sitting, he was able to drive home himself again. So the coughing and wheezing cleared quite fast. He decided to quit diving after this happened.
The other was a younger diver, diving in very cold water, 3 degrees C. Also diving on a ccr, but this time a CE-unit, Inspiration like I dive. Diver was coughing and feeling could not get enough air, but was able to get out of the water herself. The couging and wheezing lasted a few hours, but was not that bad that a doctor was visited (and it was a long walk back to the car to get all the stuff in it). This diver continoued diving and although we lost each other a little bit out of sight (just sometimes contact over social media), 1-2 times a week diving is still done and also deep cold water technical diving on ccr.
In both cases, headache was not meant.
I have had my first real CO2 hit a few weeks ago, after diving ccr for over 10 years with all kind of extreme technical diving on ccr. I was diving my Inspiration ccr, the unit I own for over 10 years now, BMCL, moderate temperature water (8 degrees celcius whichs is for us in winter warm), but flooded my drysuit completely at 65m (probably a helmet was the cause, because it was required at surface here and I did not check due to this the neckseal). Because of this, my feet got too heavy for a normal horizontal swim, so it was very hard to swim the way back to the exit (was overhead), I did not want to stirr everything up. At 45m, a horizontal passage of about 125m, I was breathing very fast and got a headache, a horrible headache, and I did some coughs, but I felt I was out of breath. I decided to bailout as I knew what was wrong. Around 12m, the breathing seemed to be more or less normal again. At 6m I felt ok again, except still headache. After the dive I was able to get out of the water myself, was very heavy because my drysuit was full of water, walked the 250m to the car myself. Did some coughs because I was very cold. Changed my clothes, but did not have dry underwear, so was still not completely dry when I walked back for my bailoutcylinders. But did al myself. Never had a feeling of wheezing or such things. I was still partly wet and cold when we had after the dive a tour in the dry part of the mine, and even after a shower I still had a headache, the headache lasted hours.
The next day I did the same dive again on the same unit, but with new sorb of course, and did not flood my drysuit
And happely, all went well.
So from what I can remember as main thing from the CO2 hit was the extreme headache under water (at surface it was already less, but not gone), and that it lasted for hours after surfacing. Under water, it felt like I breathing too fast like I was running fast, and this went quite fast ok again after bailout. There was no sign of wheezing. The rate of breathing was very high. The 2 cases of IPE I have seen did not have any headache, and the wheezing was there present, also a lot of coughing for 1-2 hours after surfacing. They decribed it as not getting enough air and water in the lungs. But there was no CO2 problem and bailing out in 1 case did not help. In 1 case, the diver was not able to help himself anymore, so needed help to swim to surface and get out of the water. When I surfaced after bailing out, I walked 3 times back to the water to get my own cylinders out of the water, I hold a camera from another diver and then I walked back to the car with my fins and camera in the hand. So was still able to do things, even if I was cold and heavy and had a headache.
